Witch:
Any person with the ability to change the world with their supernatural powers.

White witch:
Any person with the ability to change the world with their supernatural powers, but for the power of good.

Dark Witch:
Any person with the ability to change the world with their supernatural powers, but for the power of bad.

The Charmed Ones:
The most powerful witches in the world. These are the three girls themselves (either Prue, Piper, Phoebe or Piper, Phoebe and Paige). This is what the witches are constantly referred to by the supernatural world.

Spell:
A few pieces of poetry-type words that resolve any demonic or warlock-type dilemma. They usually require some sort of objects involved, along with speaking the specified words. A "spell" gets rid of any demons or warlocks.

Vanquish:
To completely get rid of any demon or warlock, using a spell.

The Book of Shadows:
The book with all The Charmed Ones' spells, in addition to supplying potions and stories etc. This is what they use to vanquish demons with help from past witches, who contributed to the book in their own ways. Also, The Charmed Ones' have the ability to add any new spells at any time. Most demons/warlocks have tried to steal the book but only one has gotten it out of the house so far.

Personal gain:
Using one's magic to personally benefit themselves. Personal gain ALWAYS results in something bad happening. This is why witches are expected to only use their magic to help innocents, not to help themselves.

The Underworld:
The place where anything bad or evil lives.

Telekinesis:
The magical ability to move objects with the mind.

Astral Projection:
The magical ability to use two different bodies to transfer from one place to another. The first, true body, places its head down while the the second travels to the other place. It then returns to the true body after a limited amount of time.

Temporal Stasis:
The magical ability to stop time from moving forward with the hands. This power is also known as "freezing". The power can be strengthened and given the ability to unfreeze particular demons' body parts too.

Particle Manipulation:
The magical ability to speed molecules up to such a point that they explode.

Premonition:
The magical ability to see into the past and into the future. Phoebe is able to do so when she touches any object of person, which then triggers the vision.

Levitation:
The magical ability to move through the air. This power is similar to the witches' myth of flying.

Charge:
Any witch that has a whitelighter, with whom they've been assigned to protect them.

Orbing:
A Whitelighter's magical ability to move from place to another, assisting them into finding their charges quicker.

Teleorbing:
Paige's ability to call for an object and simply receive it through her hands.

Whitelighter:
An immortal with the magical ability to heal witches by placing their hands on their wound. They are specially assigned to help particular witches, whom they call "charges". They also have the ability to orb.

Darklighter:
The bad version of a whitelighter. They are assigned to kill whitelighters and their charges. They usually use a crossbow to kill their victims.

Demon:
Any immortal with any special magical ability, wanting to rid the world of all goodness. In order to do this, they try to kill any witch that tries to protect the world from evil.

Warlock:
Any male with any sort of magical ability, mainly using it for the power of bad.

The Elders:
The whitelighter committee that provide whitelighters and witches with any help they require. They usually always know about any current, past or future demons/warlocks.

The Source:
The Source of all Evil. He is who created the evil in the world and has the ability to constantly defeat The Charmed Ones and all witches. However, they have now defeated him successfully.